The invention is directed to a process for the continuous enzymatic conversion of .alpha.-hydroxycarboxylic acids into the corresponding optically active .alpha.-aminocarboxylic acids in an enzyme reactor in the presence of nicotinamide-adenine-dinucleotide (NAD.sup.+ /NADH), of increased molecular weight through bonding to a water soluble high molecular weight material, a dehydrogenase specific for the .alpha.-hydroxy-carboxylic acid employed, a dehydrogenase specific for the corresponding .alpha.-amino acid and ammonium ions.
There is already known a process for the continuous production of alanine from a lactate in an enzyme reactor in the presence of a nicotinamide-adenine-dinucleotide (NAD.sup.+ /NADH) of increased molecular weight through bonding to a water soluble dextran, lactate dehydrogenase, alanine-dehydrogenase and ammonium ions (K. Mosbach and P. O. Larsson in Enzyme Engineering BIII, pages 291 to 298). Our own experiments, however, have shown that this known process cannot be carried out continuously over a long period of time because the conversion to alanine after a relatively short period of time falls off sharply until finally the conversion comes to a complete stop and no more alanine is formed.